Heliothermal flat collector module having a sandwich structure

ABSTRACT

A self-supporting heliothermal flat collector module includes a sheet metal panel; a register-type arrangement of capillary tubes separated from one another for the flow of a fluid medium that lies on the rear side of the sheet metal panel opposite that to be irradiated; and a thermally-insulating insulation core also positioned on the rear side. According to the invention, the capillary tubes of the register-type arrangement are placed into contact with the surface of the thermally-insulating insulation core, and the thermally-insulating insulation core is attached to the sheet metal panel by means of an elastic adhesive layer, whereby the capillary tubes are at least partially embedded into the adhesive layer between the sheet metal panel and the insulation core.

The invention relates to a self-supporting heliothermal flat collectormodule that includes:

-   -   A sheet metal panel,    -   A register-type arrangement of capillary tubes separated from        one another for the flow of a fluid medium that lies on the rear        side of the sheet metal panel opposite that to be irradiated,        and    -   A thermally-insulating insulation core also positioned on the        rear side.

A flat collector module of this type is known from DE-PS 100 43 295 bythis Applicant. This patent basically provides for the capillary tubesto be attached to the sheet metal panel by means of surface sprayingwith fluid metal particles. An adhesive connection of the sheet metalpanel configured with the capillary tubes to the foam insulation coremay also be taken from DE-PS 100 43 295, but in any case, the details ofthe adhesive connection are not specified.

Such an adhesive connection presents a technical problem in heliothermicflat collector modules since the joining parts possess varyingelasticity modules, and thus multi-axis tension components may arise. Inparticular, the sheet metal panel exposed to solar irradiation may bestrongly warmed and deformed. Resultantly, the adhesive connection maybe at least partially destroyed, and the contact between the capillarytubes and the sheet metal panel may be interrupted.

It is the object of the invention to prevent the above-mentioneddisadvantages, and to provide a self-supporting heliothermic flatcollector module of the type mentioned at the outset in which theinsulation core may be connected to the sheet metal panel, particularlyone of a titanium-zinc alloy, without tension across a wide temperaturerange.

This object is achieved by a self-supporting heliothermic flat collectormodule of the type mentioned above in which

-   -   the capillary tubes of the register-type arrangement are placed        into contact with the surface of the thermally-insulating        insulation core, and    -   the thermally-insulating insulation core is attached to the        sheet metal panel by means of an elastic adhesive layer, whereby        the capillary tubes are at least partially embedded into the        adhesive layer between the sheet metal panel and the insulation        core.

Each of the capillary tubes may be inserted into a slot worked into thethermally-insulating insulation core whereby the capillary tubesessentially lie flush with the insulation core, or extend from theinsulation core by a certain distance, where said distance essentiallycorresponds to a thickness dimension of the fluid adhesive layer beforehardening.

Alternatively, the capillary tubes in the register-type arrangement maybe laid directly onto a flat surface of the thermo-insulating insulationcore.

In both cases, the thermo-insulating insulation core may at least bebound to the sheet metal panel by means of the elastic adhesive layer.This means that the peak areas of the capillary tubes facing the sheetmetal panel may be in direct contact with the sheet metal panel withoutthe adhesive reaching the peak areas. The capillary tubes may also becompletely surrounded by adhesive, particularly if the adhesive hasdistinguishing thermo-conductive characteristics. These characteristicsmay be provided to the adhesive by, for example, mixing in a metalpowder.

It is further conceivable to mix fibers of short pile lengthhomogenously so that an increased degree of wear resistance or stabilityof the adhesive layer results. These fibers might possess a length of,for example, between 0.5 and 3 mm. Glass fibers are particularly suitedto this application.

The flat or slotted surface of the insulation core may include numerousrecesses to receive adhesive substances that are still moist thatpreferably extend to the slot depth or slightly exceed it. This measurecan contribute to the stability of the bond. The recesses may, forexample, be produced by impression from a bristle roller, a potentiallyheated stamp, or similar.

The thermally insulating insulation core may be of foam, particularly ofpolystyrene or polyurethane hard foam, or of a fibrous material such asmineral wool.

Since the adhesive properties of plastics, including hard foams, aresignificantly limited in comparison to those of metals, reactionadhesives operating on the adhesion bond principle are used fairlyexclusively. Diffusive adhesion is not suitable because of thenon-permeability of the sheet metal panel.

Thus, the adhesive layer may be formed, for example, of an organic,chemically curing single-component adhesive based on meth-acrylate. Theadhesive layer may also be formed of other adhesives that distinguishthemselves by their good bond to metals and plastics. For this, reactionadhesives based on styrene co-polymerization or elastomer polyurethaneresins are used. The significant point is that the adhesive layerremains permanently elastic after hardening, and does not begin to flowbecause of subsequent solar irradiation. The deformation capacity of theadhesive layer thus produced and hardened allows compensation of tensioncomponents.

The sheet metal panel may be produced as one piece with two angled,arc-shaped edge profiles by means of which a stair-step configuration ofthe roof surface may be achieved.

The sheet metal panel may also be produced as one piece with twoopposing edges bent at an angle to connect the sheet metal panels to oneanother in a folding technique.

The flat collector module based on the invention may be provided with atleast one plank or plate shaped stiffening element that is positioned ona side of the insulation core facing away from the sheet metal panel.

In another embodiment, a plastic or metal cassette may be provided onthe insulation core that includes two opposing edges bent outwards, bymeans of which the plastic or metal cassette is supported on theunderside of the sheet metal panel. An elastic body such as foam orrubber strips, or an elastic adhesive band, may lie between the sheetmetal panel and the bent edge of the metal cassette. The material of theelastic body must, however, be protected against aging and weathering.

The capillary tubes are of metal, preferably of copper or stainlesssteel. Use of metal-coated plastic tubes or uncoated plastic tubes alongthe periphery instead of metal ones is not excluded.

If the insulation core is adequately strong, and the adhesive bondproduced between the insulation core and the sheet metal panel isadequately elastic, the metal cassette or the lower stiffening elementis not required.

It is of great advantage that the thermal contact between the tubesystem be uninterrupted, since the capillary tubes are embedded into theadhesive layer, and are compressed together by means of the sheet metalpanel and the insulation core. This prevents the formation ofcondensation and electro-chemical corrosion.

Of course, the flat collector modules may also be used to cool aparticular space, since heat may be surrendered via the collector.Additionally, there is the option of using the heat energy thus acquiredto melt snow in winter. For example, a combined,automatically-controlled technique may be chosen in which so-calleddirect heating may be supported by flat collector modules.

It is expressly stated that the flat collector module based on theinvention is a low-temperature collector in which no “greenhouse effect”occurs, i.e., no additional transparent coverings are present on theside of the sheet metal panel to be irradiated that would normally forma sealed space to be heated. The sheet metal panel is thus directlyexposed to the rays of the sun.

Embodiment examples of the invention are shown in detail in thefollowing by means of illustrations, which show:

FIGS. 1 and 2 a cross-section of a flat collector module in twoembodiment examples, in schematic representation;

FIG. 3 an enlarged detailed view of the cross-section in FIG. 2;

FIG. 4 positioning of an elastic body between the sheet metal panel anda metal cassette;

FIG. 5 a flat collector module suitable for connection using a foldedtechnique, in schematic representation;

FIG. 6 a schematic cross-section of a stair step roof with built-in flatcollector modules, in cross-section; and

FIG. 7 the flat collector module per FIG. 3 in a perspective, schematicview.

FIGS. 1 and 7 show a flat collector module 10.1 that consists of a flat,rectangular sheet metal panel 1, a register-type arrangement 30 ofcapillary tubes 3.1, . . . , 3.n extending parallel to one another, anda thermally insulating insulation core 4 of polyurethane hard foam. Theinsulation core 4 possesses a thickness of 25 mm. The material of thepre-weathered and thus darker sheet metal panel 1 is an alloy oftitanium and zinc, here a product of the Applicant, RHEINZINK GmbH & Co.KG in Datteln, Germany. Surface treatment allows achieval of a highdegree of absorption since less reflection occurs.

The sheet metal panel 1 is of the following dimensions:

-   -   length 3,000 mm;    -   width 400 mm;    -   thickness 0.8 mm.

Further, the sheet metal panel 1 includes two angled, arc-shaped margins16, 17 that serve for attachment to adjacent sheet metal panels in orderto form a stair step roof 40 per FIG. 6.

Each of the plastic capillary tubes 3.1, . . . , 3.n possesses an outerdiameter of about 2.5 to 3.5 mm. The capillary tubes 3.1, . . . , 3.nextend at a uniform separation A of about 8 to 15 mm from one another.Thus, about 30 parallel-lying capillary tube sections may be mounted ina single flat collector module 10.1 of 400 mm width.

The sheet metal panel 1 is bonded to the insulation core 4 by means ofan elastic adhesive layer 2 that possesses a thickness not exceeding theouter diameter of the capillary tube. A fluid adhesive is sprayed onto ahorizontal surface 5 of the insulation core, and then the entirearrangement 30 of capillary tubes 3.1, . . . , 3.n is immediately laidwith the sheet metal panel 1 and pressed until the capillary tubes areembedded.

In this case, a cold-hardening single-component polyurethane-baseadhesive is used, a product of Sika GmbH, Stuttgart. The adhesive layer2 remains elastic after hardening.

Overall, a new type of flat collector module has been created thatincludes a form-fit but elastic bond of the insulation core 4 to thesheet metal panel 1 that is formed by the adhesive layer 2 thatsurrounds the capillary tubes in contact with the sheet metal panel. Thecapillary tubes 3.1, . . . , 3.n are also elastic, and thus may givewhen under tension.

The relatively thin insulation core 4 of polyurethane hard foam providesadequate strength to the bond so that it may be laid directly on theroof battens of the roof sub-structure (see FIG. 6).

Through the use of the adhesive bond with embedded capillary tubes andthe selection of insulation materials and their thickness, anadvantageously low thickness of the flat collector module is achieved.In this case, it is 25 mm. In another embodiment (reference index 10.2)shown in FIGS. 2 through 4, slots 14 are worked into the surface 5 ofthe insulation core 4 to receive the capillary tubes 3.1, . . . , 3.n.The capillary tubes extend out over the insulation core 4 by a smallamount H=1.5 mm, which thickness corresponds to a thickness dimension Dof the still fluid adhesive layer 2 before hardening.

Further, FIGS. 2 and 4 show a metal cassette 20 (here, an aluminumplate) surrounding the insulation core 4 that stiffens the entire bondwithout suffering loss of elasticity of the adhesive bond. The metalcassette 20 includes two opposing edges 21 angled outward andmirror-symmetrical to each other that rest on the underside 11.2 of thesheet metal panel. Elastic bodies 22, each arranged in the form of asoft foam strip between the sheet metal panel 1 and the angled edges 21of the metal cassette 20 have the task of preventing thermal transferand enabling the relative displacements of the sheet metal panel and themetal cassette. The metal cassette 20 is bonded in points to theinsulation core 4.

Further, FIG. 2 shows numerous recesses 6 that are formed into thesurface 5 of the insulation core 4 by the pressure force of a bristleroller (not shown) heated to about 200° C. The fluid adhesive flows intothe recesses and hardens there.

FIG. 5 shows a further flat collector module (reference index 10.3) thatdistinguishes itself from the flat collector module shown in FIG. 1 inthat the sheet metal panel possesses two angled bent edges 13.1, 13.2instead of the arc-shaped edges to connect the sheet metal panels to oneanother in a folding technique. Further, the side of the insulation core4 facing away from the sheet metal panel 1 is supported by aplate-shaped stiffening element 23. This stiffening element is also ofaluminum plate, and is bonded to the insulation core 4. Reference IndexList  1. Sheet metal panel  2. Adhesive layer  3.1 . . . 3.n Capillarytubes  4. Insulation core  5. Surface  6. Recess 10.1; 10.2; 10.3 Flatcollector module 13.1, 13.2 Edges 14. Slot 16. Edge 17. Edge 20. Metalcassette 21. Edge 22. Body 23. Stiffening element 26. Surface 30.Arrangment 40. Stair step roof A Separation D Thickness dimension H Anamount T_(N) Slot depth

1. In a self-supporting, heliothermal flat collector module, including:a sheet metal panel, a register-shaped arrangement of capillary tubesseparated from one another at a distance for the flow of a fluid mediumthat lies on the side opposite the side of the sheet metal panel to beirradiated, and a thermally insulating insulation core that is alsopositioned on the rear side, the improvement wherein the capillary tubesof the register-shaped arrangement are placed in contact with thesurface of the insulation core, and the insulation core is bonded to thesheet metal panel by means of an elastic adhesive layer, whereby thecapillary tubes are at least partially embedded into the adhesive layerbetween the sheet metal panel and the insulation core.
 2. Flat collectormodule as in claim 1, wherein each of the capillary tubes of theregister-shaped arrangement is placed into a slot in the insulationcore, and wherein the capillary tubes lie essentially flush with theinsulation core or extend above the insulation core by an amount (H),which amount essentially corresponds to the thickness dimension (D) of afluid adhesive layer before hardening.
 3. Flat collector module as inclaim 1, wherein the surface of the insulation core is flat, and whereinthe capillary tubes are laid directly onto the flat surface.
 4. Flatcollector module as in claim 1, wherein the insulation core comprisesfoam.
 5. Flat collector module as in claim 4, wherein the foam comprisesfoamed polystyrene or polyurethane.
 6. Flat collector module as in claim1, wherein the insulation core comprises fibrous material.
 7. Flatcollector module as in claim 1, wherein the material of the adhesivelayer has a higher thermal-conductivity coefficient than the material ofthe insulation core.
 8. Flat collector module as in claim 1, wherein theadhesive layer is formed of an adhesive based on meth-acrylate.
 9. Flatcollector module as in claim 1, wherein the slots possess a triangular,rectangular, oval, partially-round, or Ω cross-section.
 10. Flatcollector module as in claim 1, wherein the capillary tubes comprise amaterial selected from the group consisting of metal, peripherallymetal-coated plastic, and of non-coated plastic.
 11. Flat collectormodule as in claim 1, wherein the surface of the insulation coreincludes numerous recesses to receive the adhesive.
 12. Flat collectormodule as in claim 11, wherein the surface is provided with slots of agiven depth, and the recesses extend essentially to the slot depth, orextend slightly past it.
 13. Flat collector module as in claim 11,wherein the recesses are formed by the pressure of a bristle roller orsimilar device.
 14. Flat collector module as in claim 1, wherein thesheet metal panel is formed of one piece with two angled, arc-shapededge profiles.
 15. Flat collector module as in claim 1, wherein thesheet metal panel is formed of one piece with two opposing, angled edgesto connect the sheet metal panels to one another in a folded technique.16. Flat collector module as in claim 1, wherein the side of theinsulation core facing away from the sheet metal panel is supported by aplate-shaped stiffening element.
 17. Flat collector module as in claim1, wherein the insulation core is partially surrounded by a plastic ormetal cassette.
 18. Flat collector module as in claim 17, wherein themetal cassette includes two opposing margins angled outwards so that anelastic body is positioned between the angled margin of the metalcassette (20).
 19. Flat collector module as in claim 18, wherein theelastic body is a foam strip or adhesive band.
 20. Flat collector moduleas in claim 1, wherein the sheet metal panel comprises a titanium-zincalloy.
 21. Flat collector module as in claim 1, wherein the modulepossesses an overall thickness, including insulation core, in the rangeof 10 mm to 50 mm.
 22. Flat collector module as in claim 1, which isinstalled in a stair step roof, whose surface consists of sheet metalpanels connected to one another.
 23. Flat collector module as in claim1, wherein the module possesses an overall thickness, includinginsulation core, in the range of 25 mm to 35 mm.